Hardware

The NAOMI shares the same basic system architecture as the Dreamcast, with both systems using the same HitachiSH-4 CPU and YamahaAICA based sound system, along with different revisions of the PowerVR Series 2 GPU architecture. While the CPU of the NAOMI and Dreamcast operate at the same clock frequency, the NAOMI packs twice as much system and graphics memory, four times as much sound memory, a faster PowerVR2 graphics processor, faster VRAM bandwidth,[n 1] and FPGA with additional processing. Multiple NAOMI boards can also be 'stacked' together to achieve better graphics performance, or for a multi-monitor setup.

After The House of the Dead 2, a newer revision of the PowerVR2 graphics chip was used in subsequent NAOMI systems.[2] According to VideoLogic's president and CEO, Hossein Yassaie, in September 1998: "With Dreamcast, PowerVR set out to create a new standard in 3D graphics for console gaming; now with Sega’s Naomi, we will deliver unprecedented levels of 3D performance to arcade systems".[4]

Another key difference between NAOMI and Dreamcast lies in the game-media - the NAOMI primarily uses ROM PC (printed circuit) boards (i.e. large game cartridges) with up to 168 MB of usable data (more expensive but with faster loading), while the Dreamcast uses GD-ROM optical-storage with up to 1GB of storage (at the expense of load times). The NAOMI was extended in 1999 so that it could interface with GD-ROM-based arcade games. This system uses standard PC SDR-DIMM modules which are battery backed-up for storing game data. The game data is read from the GD-ROM at bootup, stored onto the SDR RAM to which the NAOMI reads from during game. This leaves less wear on the GD-ROM drive as it's only used when the memory is empty or corrupted, else it will use the SDR RAM for boot-up every subsequent power on after checking the data integrity. If the battery fails, the system is left turned off for several days or the game GD-ROM is changed, the game will be reloaded from the GD-ROM drive.

Along with the standard version, three more variants also exist:

First Edition — The initial release of NAOMI hardware was housed in an aluminium shell, similar in design to some versions of the earlier Model 2 and Model 3 system hardware. This version is known to be used in House of the Dead 2 arcade machines, with the game ROM board pre-installed inside the case. It is unknown whether this is a unique hardware variant specifically for House of the Dead 2, or whether it is compatible with later NAOMI releases. This prototype uses an earlier revision of the PowerVR2 graphics processor.[2]

Multiboard — Several NAOMI motherboards joined onto a single board which connects the multiple boards together to created a more powerful parallel processing system.

NAOMI boards can be used in special game cabinets (NAOMI Universal Cabinet) where a theoretical maximum of sixteen boards can be used in a parallel processing format.

The NAOMI multiboard setup uses a different BIOS chip than a regular NAOMI to handle all the boards but the whole system only uses one copy of the game cartridge, of which only four games were released.

Technical Specifications

NAOMI Specifications

See Sega Dreamcast technical specifications for more details on the capabilities of the general Dreamcast/Naomi hardware architecture, though the specifications for the Naomi differ from the Dreamcast in various ways, as listed below.[2]

Note: Main RAM also used to store polygon display lists. Textures transferred directly to VRAM. Textures can be streamed directly from high-speed ROM cartridge.[27] Main RAM can also optionally be used to store textures.

NAOMI GD-ROM Specifications

The NAOMI GD-ROM, released in 1999, is identical to the standard NAOMI, but uses GD-ROM discs for storage instead of ROM cartridges. It comes with a DIMM Board, which is very similar to a ROM cartridge, but with RAM instead of ROM. When a game is installed, the GD ROM content is loaded onto the DIMM Board RAM, so that the game data runs from the DIMM Board rather than the GD-ROM disc.

Bandwidth

NAOMI Multiboard Specifications

The NAOMI Multiboard, released in 1999, stacks together multiple NAOMI system boards for parallel processing in a single arcade system, ranging from 2 to 16 system boards. Since the 16‑board variant is not known to have been used by any games, the following specifications are for the 2‑board and 4‑board variants:

History

The NAOMI debuted at a time when traditional arcades were on a decline, and so was engineered to be a mass-produced, cost-effective machine reliant on large game ROMcartridges which could be interchanged by the arcade operator. This is contrary to systems such as the Model 3, in which each board, despite sharing largely the same specifications, would be bespoke, with the built-in ROMs being flashed with games during the manufacturing process. This is not the first time such an idea was utilised by Sega, but never before had technology been used for a cutting-edge Sega arcade specification.

Unlike most hardware platforms in the arcade industry, NAOMI was widely licensed for use by other manufacturers, many of which were former rivals to Sega, such as Taito, Capcom and Namco. It is also one of the longest-serving arcade boards, being supported from 1998 to 2009. It is a platform where many top-rated Sega franchises were born, including Virtua Tennis, Samba de Amigo, Crazy Taxi and Monkey Ball.

Promotional material

Press Kit (1998)

Photo gallery

First Edition

Sockets, with open lid

Inside, internal ROM board removed

Model number

Outer case, back

Outer case, right

Outer case, left

Motherboard, top

Motherboard, bottom

Motherboard, side

Main version

Top of the motherboard

Bottom of the motherboard

Sockets

Full System

NAOMI Case

GD-ROM slot

DIMM Module + Key

Notes

↑ Scaled for high-end arcade technology,[14] with parallel ISP cores and increased PE processing elements within processor.[15] NAOMI has average fillrate of 1 gigapixel/sec,[4] twice that of the Dreamcast's average 500 megapixels/sec fillrate.[16]